Aberrations in a microscope and specimen have a negative effect on microscopic imaging. As is known, these aberrations may be corrected using adaptive optics in the pupil plane. However, this is only true for wide-field imaging under certain conditions. In this case, it is not possible to optimally correct aberrations that vary across the image field, since the pupil in which the correcting elements are normally placed is the same for all image areas.
Known techniques for correcting aberrations using adaptive optics are employed inter alia in laser scanning microscopy, wherein the adaptive optics may be adjusted for different scan positions. Local image regions are positioned by the scan and may be corrected in the pupil plane in temporal sequence.
According to the solutions of the prior art, for wide-field microscopy the technique is possible only for correcting the mean errors across the entire image field. Thus although an improvement of individual regions is possible, this is at the cost of a worsened image correction in the other areas.
In “Multiple-Field Approach for Aberration Correction in Miniature Imaging Systems Based of Wafer-Level Production” (Eric Logean et al in Proc. SPIE 8667, 1913), a solution is presented in which a plurality of lenses having different focal lengths are used in order to correct field-related defocus terms in non-planar-corrected imaging systems. This solution has the disadvantage that only a deterministic system correction is possible. Adaptively changeable specimen aberrations cannot be corrected.
Proceeding from the disadvantages of the solutions in the prior art, the underlying object of the invention is to refine an arrangement for correcting aberrations across an extended image field on a microscope, which arrangement permits improved corrections of aberrations for wide-field microscopy, even across large image areas, and may also be used in scanning microscopes at high scan speeds.
In accordance with the invention, this object is attained with an arrangement of the type described in the foregoing using the features of patent claim 1. Advantageous embodiments are provided in subordinate claims 2 through 11.
In accordance with the invention, the pupil stop is disposed between the lens and the tubular lens unit. The optical element for optical-geometric separation of different image field regions is arranged in or near the intermediate image plane, wherein each individual element of the optical element for optical-geometric separation of different image field regions performs a pupil imaging, defined by the dimensions of the covered area of the intermediate image, and undertaken using at least one pupil imaging lens that may be part of the element for optical-geometric separation, so that a distribution of sub-pupils occurs. Each sub-pupil is allocated to the angle distribution from the associated image field region.
In one advantageous embodiment, the optical element for optical-geometrical separation of different image field regions is embodied as a lens array.
In another advantageous embodiment, the optical element for optical-geometric separation of different image field regions is to be embodied as a deflection element array, wherein in this case blazed gratings, the grating constant and/or blaze angle of which are different for different image field regions, or facet mirrors having different angles of incidence for the different image field regions are possible.
When using blazed gratings, an element for correcting chromatic errors that occur due to the wavelength dependence on the deflection is also necessary.
The arrangement may be coupled both to a wide-field microscope and to a scanning microscope.
Thus it is possible to separate and allocate the pupils to different image areas, so that the arrangement permits individual and yet simultaneous correction.